"Stage hunk" button is gone

After updating to 1.6.10, the "Stage hunk" button - the most important button and by far the biggest reason I got hooked on SourceTree - is gone. So is the "Stage lines" that used to appear after I select some lines. Rolled back to 1.6.8 and they're back.

Since this wasn't in the release notes, I'm hoping that this is a bug and not an intentional change.